Hydro-electric installation

ABSTRACT

A hydroelectric installation, comprising a hydraulic machine, such as a turbine, pump or pump turbine, wherein the rotor is coupled to the shaft of a synchronous alternating current electrical machine operating as an alternator, or as a motor. When operating as a turbine, the installation includes at least one set of rectifiers transforming the alternating current produced by the alternator into direct current. When operating as a pump, the installation includes at least one undulator transforming the direct current supplied by the electric line into alternating current and supplying the motor. In both instances the installation comprises a pilot device controlling the mechanism regulating the quantity of water flowing through the turbine, or the frequency of the current output of the undulator to maintain at any instant, the predetermined speed of rotation of the rotor of the machine regardless of the value of the hydraulic head existing at that moment.

United States Patent Adrien Merenda HYDRO-ELECTRIC INSTALLATION 9Claims, 1 Drawing Fig.

US. Cl 417/237, 290/52, 415/500 Int. Cl ..F04b 41/04, H02k 7/18, FOld15/10 Field of Search 417/237, 410, 411, 423, 424, 22; 290/52; 415/500,47

' References Cited UNITED STATES PATENTS 2,246,472 6/1941 Sharp 290/522,962,599 11/1960 Pirkey 415/500 X 3,372,645 3/1968 Willi 415/500 XABSTRACT: A hydroelectric installation, comprising a hydraulic machine,such as a turbine, pump or pump turbine,

wherein the rotor is coupled to the shaft of a synchronous alternatingcurrent electrical machine operating as an alternator, or as a motor.When operating as a turbine, the installation includes at least one setof rectifiers transforming the alternating current produced by thealternator into direct current. When operating as a pump, theinstallation includes at least one undulator transforming the directcurrent supplied by the electric line into alternating current andsupplying the motor. In both instances the installation comprises apilot device controlling the mechanism regulating the quantity of waterflowing through the turbine, or the frequency of the cur rent output ofthe undulator to maintain at any instant, the predetermined speed ofrotation of the rotor of the machine regardless of the value of thehydraulic head existing at that 1,047,557 12/1912 Owens 417/22X moment.

521$: a s l eov F'HEAEENOR eovenuon sweet; SENSOR I L SPEED c|Rcu|'rSENSOR ,BREAKERS i 16 17 re l i ELECTRICAL eovrnuon MACHINE UNDULATOR-necnnzn I I 2 1s 20 .4 23 29 7 l 22 FREQUENCY E' -EE UNDULATOR DRECTIFIER-1' i t I I 24 25 CIRCUIT g6 BREAKERS25 27 I l HYDRO-ELECTRICINSTALLATION in most hydroelectric installations including an upperreservoir of water, the level of the water often varies causingmodifications in the head, which are important, even when expressed inrelative values in relation to the head itself. For a given machine,such as a turbine, pump or pump turbine rotating at a given speed, thehydraulic efficiency depends to a great extent on the height of thehead, the variations of which are often very important. The loss ofproduction due to a fall in the hydraulic efficiency of the machine-isalso very important. It is therefore expedient to take all possiblemeasures in order that the machine operates with a good hydraulic efficiency in spite of the natural variations of the head.

Various solutions have been applied tending to attain this result. It isfairly common, for example, to construct electrical machines, motors orgenerators, synchronous, three-phase,

made in such a way as to be able to rotate at at least two dif-' ferentspeeds despite the fact that the alternating current supply is atconstant frequency. Thus, to each of the speeds of rotation correspondsa different value of the head for which the hydraulic efficiency isoptimum. With such a machine it is sufficient to choose the speed ofrotation of the hydroelectric unit which corresponds best to thehydraulic head existing at the moment considered. The production of suchan electrical machine is, however, difficult and the extremely limitednumber of speeds of rotation possible, generally only two, are

' insufficient in most cases and especially in all cases where therelative variations of the head are important.

The object of the present invention concerns the production ofhydroelectric machines capable of rotating at all the necessary speeds,permitting maintenance at all times of the optimum efficiency of theinstallation regardless of the value of the hydraulic head beingconsidered. In other words, itconcems a hydroelectric installationconnected to at least one direct current electrical line, in which thehead is submitted to appreciable variations, comprising a hydraulicmachine, such as a turbine, pump or pump turbine, of which the rotor iscoupled to the shaft of a synchronous alternating current electricalmachine operating as an alternator or as a motor. The installationcomprises further, when operating as a turbine, at

least one set of rectifiers transforming the alternating currentproduced by the alternator into direct current and when operating as apump, at least one undulator transforming the direct current supplied bythe electric line intoalternating current and supplying the motor,characterized in that the installation includes a pilot devicecontrolling the mechanism regulating the quantity of water flowingthrough the turbine, or the frequency of the current output of theundulator to adapt, at any instant, the speed of rotation of the rotorofthe machine as a function of the value of the hydraulic head existing atthat moment, the speed chosen in such a way that the efficiency of themachine remains appreciably at its optimum value despite the variationsof head.

Another object of the present invention concerns reversible machinessuch as pump turbines which, in addition to the natural variations ofthe head are submitted to other variations according to the way in whichthey operate. When a hydraulic machine operates as a turbine, the nethead at disposal' between the inlet and the outlet of the turbine isequal to the gross head less the losses due to the friction of the waterin the pipeline. On the other hand, when the machine works as a pump itmust supply a pressure equal to the gross head increased by the pressurelosses of thewater in the pipeline. Thus, for the same natural head, thehead at disposal for the operation of the turbine is different from thepumped head to be supplied when the machine is in service as a pump. Thedifference is roughly equal to the double of the sum of the losses inall of the. pipelines.

The relationships connecting the speed of rotation and the head in ahydraulic machine are known. It is also generally known that the fastera pump turns the higher the head which can be delivered. It is thisproperty that is utilized in the present invention.

However, the realization of an electrical machine with a goodefficiency, of high power, supplied by or supplying a high-voltage linecapable of working over a whole range of speeds of rotation and finallynot necessitating excessive main tenance is not yet possible. However,by employing a synchronous electrical machine, conventional motor oralternator, the objective sought can be attained. In fact the progressmade recently in the construction of current rectifiers, transformingalternating current into direct current and in the construction ofundulators carrying out the reverse, that is transforming direct currentinto alternating current, allow the consideration of the use of suchelements which are economical and dependable even for very high voltagesand for high powers. ln intercalating such apparatus, that is arectifier and an undulator between a synchronous alternating currentelectrical machine and an alternating current network, this amounts todecoupling the frequencies, that of the machine being able to bedifferent from that of the network. The electrical connection servesonly for the passage of the power, that is of the energy, so there is nolonger a synchronization of the machine and the network. This decouplingof the frequencies thus permits the hydroelectric machine to rotate at aspeed different from that which would be imposed by synchroniration withthe network and especially at the best speed, that is to say, at a speedpermitting the maintenance of the optimum efficiency despite thevariations of head which could occur.

The sole FlGURE included herewith represents schematically and as anexample one form of execution of the installation. This hydroelectricinstallation is composed of the following principal elements:

2. upper storage reservoir;

2. supply pipeline in the case of operation as a turbine: deliverypipeline in the case of operation as a pump;

3. the hydraulic machine: turbine, pump or pump turbine;

4. suction pipe;

5. reservoir: of restitution in the case of operation as a turbine, andof intake (suction) in the case of operation as a pump;

6. wicket gate mechanism, apparatus regulating the discharge of theturbine;

7'. servomotor for operation of the wicket gate mechanism;

8. governor;

9. governor headelaborating a correcting signal in function of thedifference between the real speed of the rotor of the unit and thedesired speed;

10. shaft connecting the hydraulic and electrical machines;

1 1. device measuring the speed (operation as a turbine);

12. device measuring the speed (operation as a pump);

13. governor, operation as a pump, elaborating a correcting signal infunction of the difference between the real frequency of the alternatingcurrent connecting line 15 and the desired frequency;

l4. electrical machine: alternator, or synchronous motor;

15. alternating current electric connecting line;

16. three circuit breakers;

17. three circuit breakers;

18. three circuit breakers;

l9.1'.mit undulator;

20. unit rectifier;

21. three direct current electric power lines;

22.}three direct current electric power lines;

23. three direct current electric power lines;

24. network rectifier;

25. network undulator;

26.}two circuit breakers;

27. two circuit breakers;

28. alternating current network;

29. direct alternating current line;

30. pilot device of the network undulator 25;

3 1. control device allowing the introduction of a signal of regulationof the desired speed;

32. control device allowing the introduction of a signal of regulationof the desired frequency.

The operation of the installation is as follows:

Suppose that controlled by the. position occupied by the wicket gatemechanism 6. The energy produced by the turbine which drives, by meansof the shaft 10, the rotor of the synchronous alternator 14 leaves bymeans of the electrical distribution line 15. The circuit breaker 17 isclosed whereas the circuit breakers 16 and 18 are open. This energy thenpasses through the rectifier 20 which transforms the alternating currentinto direct current and supplies the direct current distribution network21. v 1

Installations for the transport of energy at high voltage and over verygreat distances, in the form of direct current, are today more and morenumerous because, with this form of current, the line losses are greatlyreduced in comparison with those existing in a line transportingalternating current. Moreover, it is equally possible to utilize thisenergy, which is in the form of direct current, and to consume it in theform of alternating current as is the case for the great majority of theactual uses. To this effect, it suffices to close the circuit breaker27, leaving 26 open which puts into service the network undulator 25which transforms the direct current output from the unit rectifier 20into alternating current. The installation may comprise a supplementarypilot device 30 controlling the network undulator 25 in such a way thatthe frequency which said undulator delivers is precisely equal to thefrequeney of the network 28.

By this arrangement, it will be noted that the frequencies of thenetworks 28 and may be different to each other, even to a great extent.

The governor head 9 measures the speed of the unit by means of thespeed-sensing device 11 and operates, by means of the governor 8 and theservomotor 7, the wicket gate mechanism 6 in such a way that therotational speed of the rotor of the unit, shaft 10, be exactly equal tothe speed corresponding to the maximum efficiency of the machine takinginto account the head existing at the moment considered. It isunderstood that this speed varies when the head varies and can beadapted more or less continuously according to the particular case.

Generally speaking, the speed of change of the head is very low becauseit is appreciably equal to the speed of change of the level of water inthe reservoir. The greater part of the time a manual control by means ofthe device 31 is sufficient. However, this operation can be automated bymaking the value of the head act on the device 31, thus continuouslyadapting the desired speed of the unit to the variations of the head.The control circuit 7, 8, 9 intervenes continuously in order that theactual speed remains equal to the desired speed.

In the case of operation as a pump, the circuit breakers 17, 18 and 27are open whereas the circuit breaker 16 is closed. The energy comingfrom either a direct current distribution line 21 or from thealternating current network 28, passing via the intermediary of thecircuit breaker 26, also closed, and the network rectifier 24 supplies,via the undulator 19, the electrical machine 14. The installationcomprises further a regulating device 13 influencing the undulator 19 insuch a way that the frequency of the electrical current delivered by theapparatus is regulated as a function of the frequency desired,precisely, of the head, and this in the same manner as the speedgovernor head 9, in the case of operation as a turbine. The speed ofrotation of the unit is directly connected, for a synchronous electricalmachine, to the frequency of the supply current 15. To fix the speed ofrotation of the shaft 10 of the pump it is sufficient to pilot thefrequency of the output of the undulator 19. The governor 13 receivesfrom the speedmeasuring device 12 a signal of actual frequency and fromthe control device 32 a signal of the desired frequency. lt elaborates acorrecting signal which is a function of their difference and controlsthe frequency of the undulator in such a way that the speed of rotationof the pump be the best possible, taking into account the value of thehead to be supplied.

The pump turning at its correct speed sucks water from the lowerreservoir 5 and discharges it via the pipeline 2 into the upperreservoir 1.

As in the case of operation as a turbine, the system can be automated,the head intervening directly on the governor 13- to modify thefrequency of the output of the undulator.

The schematic drawing illustrates further the possibility of obtaining adirect connection by means of the line 29 and the circuit breaker 18allowing, if necessary, the direct connection of the electrical machine14 to the networkin the case where the rotational speed of the shaftallowing the optimum efflciency of the hydraulic machine is preciselyequal to the speed of this shaft if it were directly synchronized on thenetwork. The two networks are connected to each other by means of thecircuit breaker 18 and the line 19, the other circuit breakers 16 and17, 26 and 27 being open.

The operation of a pump turbine is identical, according to the case, tothe one or the other of the two types of operation described.

The above description mentions the case of alternating current machinesand networks; it is clear that it could be singlethreeor polyphasecurrent which is being considered. In the same way one could realizeelectrical machines having a number of phases different to the networkand notably a higher number, that which improves appreciably theoperation of the rectifiers.

I claim:

1. A hydroelectric installation connected to at least one direct currentelectric line in which the hydraulic head is subject to appreciablevariations, comprising a pump turbine including a rotor, a synchronousalternating current electrical machine operating as an alternator or asa motor. said machine including a shaft, means operatively connectingsaid rotor to said shaft, at least one set of rectifiers transformingthe alternating current produced by the alternator into direct currentwhen the pump turbine is operating as a turbine, at least one undulatortransforming the direct current supplied by the electric line intoalternating current and supplying the motor when the pump turbine isoperating as a pump, control means for regulating the discharge of waterthrough the pump turbine when operating as a turbine, said control meansfurther regulating the frequency of the current output of the undulatorwhen the pump turbine is operating as a pump, said control meansincluding means sensing the speed of rotation of said rotor-to-shaftconneetingmeans, whereby said connecting means is maintained at apredetermined speed of rotation regardless of variations of thehydraulic head.

' 2. An installation according to claim 1, wherein said direct currentelectric line is supplied with energy from an alternating currentelectrical network including at least one set of rectifiers and at leastone undulator acting on said direct current electric line to supply withenergy an alternating current electrical network.

3. An installation according to claim 1, wherein said hydroelectricmachine and said set of rectifiers supplying the energy to the directcurrent electric line are situated in the same geographical place.

4. An installation according to claim 2, wherein said hydroelectricmachine and said set of rectifiers supplying the energy to the directcurrent electric line are situated in the same geographical place.

5. An installation according to claim 1, wherein said alternatingcurrent electrical machine is polyphase.

6. An installation according to claim 2, wherein said alternatingcurrent electrical network supplyingthe direct current electric linewith energy through the set of rectifiers. is polyphase,

7. An installation according to claim 1, wherein the number of phases ofthe electrical network supplying said direct current electric line withenergy is different from the number of phases of said alternatingcurrent electrical machine.

8. An installation according to claim 5, wherein the number of phases ofthe electrical network supplying said direct curof phases of theelectrical network supplying said direct current electric line withenergy is different from the number of phases of said alternatingcurrent electrical machine.

1. A hydroelectric installation connected to at least one direct currentelectric line in which the hydraulic head is subject to appreciablevariations, comprising a pump turbine including a rotor, a synchronousalternating current electrical machine operating as an alternator or asa motor, said machine including a shaft, mEans operatively connectingsaid rotor to said shaft, at least one set of rectifiers transformingthe alternating current produced by the alternator into direct currentwhen the pump turbine is operating as a turbine, at least one undulatortransforming the direct current supplied by the electric line intoalternating current and supplying the motor when the pump turbine isoperating as a pump, control means for regulating the discharge of waterthrough the pump turbine when operating as a turbine, said control meansfurther regulating the frequency of the current output of the undulatorwhen the pump turbine is operating as a pump, said control meansincluding means sensing the speed of rotation of said rotor-to-shaftconnecting means, whereby said connecting means is maintained at apredetermined speed of rotation regardless of variations of thehydraulic head.
 2. An installation according to claim 1, wherein saiddirect current electric line is supplied with energy from an alternatingcurrent electrical network including at least one set of rectifiers andat least one undulator acting on said direct current electric line tosupply with energy an alternating current electrical network.
 3. Aninstallation according to claim 1, wherein said hydroelectric machineand said set of rectifiers supplying the energy to the direct currentelectric line are situated in the same geographical place.
 4. Aninstallation according to claim 2, wherein said hydroelectric machineand said set of rectifiers supplying the energy to the direct currentelectric line are situated in the same geographical place.
 5. Aninstallation according to claim 1, wherein said alternating currentelectrical machine is polyphase.
 6. An installation according to claim2, wherein said alternating current electrical network supplying thedirect current electric line with energy through the set of rectifiers,is polyphase.
 7. An installation according to claim 1, wherein thenumber of phases of the electrical network supplying said direct currentelectric line with energy is different from the number of phases of saidalternating current electrical machine.
 8. An installation according toclaim 5, wherein the number of phases of the electrical networksupplying said direct current electric line with energy is differentfrom the number of phases of said alternating current electricalmachine.
 9. An installation according to claim 6, wherein the number ofphases of the electrical network supplying said direct current electricline with energy is different from the number of phases of saidalternating current electrical machine.